OUTPUT FROM MOTOR CORTEX TO CONTRALATERAL AND IPSILATERAL HINDLIMB MUSCLES IN THE PRIMATE

Although corticospinal control of the forelimb has been heavily studied for several decades, relatively little is known about corticospinal control of the hindlimb despite its importance. The overall goal of this project is to investigate hindlimb corticospinal organization and function using methods that have been successfully used to investigate the forelimb. The first two specific aims are designed to evaluate the organization and characteristics of output from primary motor cortex (M1) to hindlimb muscles using spike triggered averaging (SpTA) of electromyography (EMG) recordings. Aim one is to determine whether postspike effects can be detected in averages of EMG activity of distal and proximal hindlimb muscles. This was done by isolating single neurons in the hindlimb representation of M1 and generating averages of EMG segments associated with the individual action potentials (spikes) of each cell. The second aim is to compare the properties of hindlimb postspike effects to forelimb postspike effects collected previously in the laboratory. The third aim is to determine the extent to which poststimulus effects, elicited by stimulus triggered averaging (StTA) in distal and proximal muscles match the postspike effects from a single cell recorded at the same cortical site. Aim four is to evaluate the organization and characteristics of output from the ipsilateral M1 to hindlimb muscles using StTA of EMG activity. In this aim, we will document the properties of poststimulus effects in hindlimb muscles from ipsilateral cortex compared to those from the contralateral cortex. Aim five is to evaluate the function of hindlimb M1 in voluntary movement by reversibly inactivating large portions of the M1 hindlimb representation using injections of the GABA-A agonist, muscimol. Three-hundred-seventy-one neurons in the hindlimb representation of M1 were isolated and tested with spike triggered averaging of EMG activity from twenty-two hindlimb muscles including hip, knee, ankle, digit and intrinsic foot muscles. Despite the presence of monosynaptic connections from corticospinal neurons to hindlimb motoneurons and the fact that the density of corticospinal neurons in hindlimb M1 is similar to that of forelimb M1 (Cheney et al. 2004), the effects in hindlimb muscles from M1 differed substantially from those of forelimb M1. Although the fraction of cells producing a significant postspike effect was similar for forelimb and hindlimb M1, the number of muscles with postspike effects (muscle field) per cell was markedly lower for hindlimb. Another striking difference was the much higher incidence of synchronous and complex effects, compared to true postspike effects, from hindlimb neurons compared to forelimb. To evaluate the strength of motor output from ipsilateral M1 cortex (Aim 4), microstimuli (120 μA) were applied a low rate (5 Hz) and served as triggers to construct stimulus triggered averages of EMG activity. Post-stimulus effects from ipsilateral M1 cortex were then compared to those from contralateral cortex obtained under the same conditions. The magnitudes of contralateral effects were far greater than the magnitudes of ipsilateral effects. In addition, there were fewer effects from ipsilateral cortex obtained at the same stimulus intensity. The organization of neurons was also quite different. For all muscles, the location of maximal output from M1 was shifted anterior and laterally in the ipsilateral cortex compared to contralateral M1. Surprisingly, the minimal onset latencies of effects from ipsilateral cortex were similar to those from contralateral cortex. In conclusion, we were able to detect clear effects in spike triggered averages of EMG activity. The output effects from single neurons in hindlimb M1 differ from those from forelimb M1 neurons in the number and strength of effects as well as the incidence of strong synchrony effects. We used stimulus triggered averaging of EMG activity to evaluate the ipsilateral connections from M1 to motoneurons. Effects from ipsilateral cortex are distinctly weaker than those from contralateral cortex. However, the onset latency of the shortest latency effects from ipsilateral cortex were similar to those from contralateral cortex suggesting that ipsilateral cortex has a minimal linkage that is as direct as that from contralateral cortex. This result suggests that at least some corticospinal neurons in ipsilateral cortex make monosynaptic connections with motoneurons in the spinal cord. We used stimulus triggered averaging data to construct maps of cortical output to different muscle groups. Comparing ipsilateral and contralateral maps revealed that the spatial distribution of neurons producing maximal output effects from ipsilateral cortex is not a mirror image of those in contralateral cortex. Rather, the best location for producing output to a particular muscle from ipsilateral cortex is substantially displaced relative to its position in contralateral cortex. This dissertation provides foundational data on the output properties of ipsilateral cortex in healthy, intact subjects. How these properties may change in relation to recovery of function following damage to contralateral M1 cortex is a question that remains for future studies

Short-Term Radiographic Evaluation of a Tri-Tapered Femoral Stem in Direct Anterior Total Hip Arthroplasty

Introduction. Direct anterior approach (DAA) total hip arthroplasty (THA) has become increasingly popular, largely due to utilization of a true internervous and intermuscular plane. However, recent literature has demonstrated an increased rate of femoral implant subsidence with this approach. Hence, different femoral implants, such as the tri-tapered femoral stem, have been developed to facilitate proper component insertion and positioning to prevent this femoral subsidence. The purpose of this study was to evaluate the subsidence rate of a tri-tapered femoral stem implanted utilizing a DAA, and to determine if the proximal femoral bone quality affects the rate of subsidence. Methods. A retrospective analysis of 155 consecutive primary THAs performed by a single surgeon was conducted. Age, gender, primary diagnosis, and radiographic measurements of each subject were recorded. Radiological evaluations, such as bone quality, femoral canal fill, and implant subsidence, were measured on standardized anteroposterior (AP) and frog-leg lateral radiographs of the hip at 6-week and 6-month postoperative follow-up evaluations. Results. The average subsidence of femoral stems was 1.18 ± 0.8 mm. There was no statistical difference in the amount of subsidence based on diagnosis or proximal femora quality. The tri-tapered stem design consistently filled the proximal canal with an average of 91.9 ± 4.9% fill. Subsidence was not significantly associated with age, canal flare index (CFI), or experience of the surgeon. Conclusion. THA utilizing the DAA with a tri-tapered femoral stem can achieve consistent and reliable fit regardless of proximal femoral bone quality

Urine Screening for Opiod and Illicit Drugs in the Total Joint Arthroplasty Population

Introduction. Recent studies have shown an increase in post-operative orthopaedic complications associated with pre-operative opioid use. It is, therefore, important to know if patients use opioids before scheduled surgery. The purpose of this study was to determine if urine drug screening (UDS) is an effective screening tool for detecting opioid and illicit drug use prior to joint arthroplasty (JA) procedures. Methods. This retrospective chart review was performed with IRB approval on 166 out of 172 consecutive patients in a community-based practice. All the patients had a pre-operative UDS prior to primary or revision JA by a fellowship trained orthopaedic surgeon between March 2016 and April 2017. Patient demographics documented opioid and illicit drug use, co-morbid diagnosis, and UDS results were collected from clinical charts. Statistical analysis was conducted using Pearson Chi-square, Fisher’s exact, McNemar test, and t-tests with IBM SPSS Statistics, ver. 23. Significant differences were p < 0.05. Results. Sixty-four of 166 patients (38.6%) tested positive for opioids. Among them, 55.0% (35/64) had no history of prescription opioid use. Significant differences were observed when comparing the test results of the UDS with the patient reported history of prescribed opioids (p = 0.001). Conclusion. With a significant number of patients testing positive for opioids without evidence of a previous prescription, UDS may be beneficial for initial risk assessment for patients undergoing JA procedures

Emergency Action Planning in Kansas High Schools

Introduction. Current evidence shows a variable rate of emergency action plan (EAP) implementation and a low rate of compliance to EAP guidelines in United States secondary schools. Compliance to emergency action plan recommendations in Kansas high schools is not known. The purpose of this study was to identify the emergency preparedness of public high school athletics in the state of Kansas and identify prevailing characteristics of schools that correlate with decreased compliance of an EAP. Methods. Athletic directors for public high schools in the state of Kansas were asked to participate in a web-based questionnaire that was emailed to each athletic director. The questionnaire identified demographics of the study population, EAP implementation rates, compliance to national EAP guidelines, access to certified medical personnel, and training received by athletics personnel. Descriptive statistics were then compiled and reported. Results. The response rate for the survey was 96% (341/355). A total of 94.1% (320/340) of schools have an EAP, 81.4% (276/339) of schools have an automated external defibrillator (AED) at all athletic venues, and 51.8% (176/340) of schools had an athletic trainer (AT) on staff. Urban schools were significantly more likely than rural schools to have an AT on staff (OR=11.10, 95% CI=[6.42, 19.18], p<0.0001), have an EAP (OR=3.69, 95% CI=[1.05, 13.02], p=0.0303), require additional training for coaches (OR=2.69, 95% CI=[1.42, 5.08], p =0.0017), and have an AED on-site for some events (OR=2.18, 95% CI=[1.24, 3.81], p=0.0057). Conclusions. Most Kansas high schools have an EAP in place and have at least 1 AED. Emergency planning should be improved through venue specific EAPs, access to early defibrillation, and additional training. Rural and low division schools have lower AT staffing and consequently are more significantly impacted by these factors. Rural and low division schools are more significantly impacted than urban and high division schools and this should be taken into account in future improvement strategies

Emergency Action Planning in School-Based Athletics: A Systematic Review

Introduction. A significant number of preventable catastrophic injuries occur in secondary school athletics. Compliance to Emergency Action Plan (EAP) recommendations is not well documented. The purpose of this systematic review was to identify compliance to EAP recommendations, access to an athletic trainer (AT) and automated external defibrillator (AED), and current legislative mandates in school-based athletics. Methods. Electronic databases were searched to identify articles that met criteria for inclusion. Studies in English that focused on adoption, implementation, or compliance with EAPs or other national guidelines pertaining to athlete health were eligible for inclusion. Quality and validity were examined in each article and data were grouped based on outcome measures. Results. Of 12,906 studies, 21 met the criteria for inclusion and full text review. Nine studies demonstrated EAP adoption rates ranging from 55% - 100%. Five studies found that EAPs were rehearsed and reviewed annually in 18.2% - 91.6% of schools that have an EAP. At total of 9.9% of schools were compliant with all 12 National Athletic Trainers Association (NATA) EAP guidelines. A total of 2.5% - 27.5% of schools followed NATA exertional heat illness guidelines and 50% - 81% of schools had access to an Athletic Trainer. In addition, 61% - 94.4% of schools had an AED available at their athletic venues. Four of 51 state high school athletic association member schools were required to meet best practice standards for EAP implementation, 7 of 51 for AED access, 8 of 51 for heat acclimation, and 3 of 51 for concussion management. Conclusions. There was a wide range of EAP adoption and a low rate of compliance to EAP guidelines in U.S. schools. Barriers to EAP adoption and compliance were not well documented and additional research should aim to identify impeding and facilitating factors